I'm trying to use the email functionality of calibre to send a book in an .epub format. For example: when I have a book in three formats (.epub, .mobi, .lit) and I choose to send that book via email (using Gmail servers, tested and confirmed), the book received through email is always in the .mobi format.

I'm using an iPad 3 and I really want to get a book in the .epub format for usage in iBooks. I looked through the preferences but didn't see anything. A little bit of Googling didn't reveal anything outright.

Can anyone help me figure out how to achieve this functionality? I'd love to be able to send it straight from calibre without exporting the .epub and emailing an attachment.

In the Calibre preferences you set what formats can be emailed as part of the email settings. Since this feature is most commonly used with Kindle books the default is almost certainly .mobi if you do not change it.